Air feed for rock drills



Feb. 26, 1935. J. c. CURTIS AIR FEED FOR ROCK DRILLS Filed June 5, 1933 2 Sheets-Sheet l Nwmm m Qmw JOHN C. Cuff/.5

INVENTOR ATTORNEY Feb. 26, 1935. cu'Rns 1,992,416

AIR FEED FOR ROCK DRILLS Filed June 5, 1933 2 Sheets-Sheet 2 JOHN C. CUE 775 INVENTOR ATTORNEY Patented Feb. 26, 1935 f fum-reoqsrA'res PATENT OFFICE,

AIR FEED FOR ROCK DRILL S John 0. Curtis, Garfield Heights, Ohio, assignor to The Cleveland Rock Drill Company, Cleveland, Ohio, a corporation of Ohio Application June 5, 1933, Serial No. 674,395 1 Claim. (Cl. 121-9) This invention relates broadly to rock .drills,

but more particularly to fluid actuated mecha nism for rock drillsof the drifter type.

One object of this invention is to provide means for cushioning the feed piston at the extreme end of its stroke withinthe cylinder.

Another object of this invention is to provide pneumatic cushioning means adapted to reduce the traveling speed of the feed piston within its 1 cylinder, when the former has reached the vicinityof one end of the latter.

Another object of this invention is to produce an improved feeding mechanism for rock drill wherein cushioning means are provided to prevent the abrupt termination of the stroke of the feed piston within its cylinder.

Other objects and advantages more or less ancillary to the foregoing reside in the specific construction and aggroupment of the elements peculiar to this structure, as will become apparent from a more complete examination of this specification. f

In the drawings which'illustrate a preferred embodiment of the invention:

Fig- 1 is a longitudinal view partly in section illustrating the machine assembly.

Fig. 2 is an enlarged cross sectional view taken in aplane indicated by line 22 in Fig. 5.

Fig. 3 is an enlarged sectional view of the right end of the feeding mechanism illustrated in Fig. 1. I

Fig. 4 is an enlarged-sectional view of a portion of the feeding mechanism, illustrating the feed piston approaching the end of its stroke.

Fig. 5 is a view similar to Fig. 4, illustrating the feed piston closer to the end of its stroke.

Referring to the drawings in which like charactersdesignate correspondingparts throughout the several views, represents a rock drill of the drifter type having a piston reciprocably mounted therein and capable to deliver its blows to a cutting tool 11. The lower portion of the cylinder of the rock drill 10, is formed with a duality of ribs 12 disposed in parallelism and capable of slidable engagement into corresponding ways 13, formed in the air feed tube or mounting 14. This feed tube is preferably formed of rectangular cross section, and has disposed within the extreme left end thereof a back head 15, secured therein by means of bolts 16. To prevent the escape of the pressure fluid between the internal wall of the feed tube and the back head, there is a packing 17, secured to the back head by means of bolts 18. Rotatably mounted within the back head 15, there is a throttle valve 19 formed and nut 39.

with a shank protruding to the exterior of the feed tube and adapted to receive a handle 20. The throttle valve 19 is-formed with a centrally disposed bore or chamber 21 into which pressure fluid may be admitted through an inlet connection or conduit 22, which is secured to the side of the feed tube, by a nut 23. Leading from the chamber 21 to the peripheral wall of the throttle valve 19, thereare two inlet ports 24 and 25 located in juxtaposed vertical plans. Disposed within each of these plans, the throttle valve is also provided with two circular recesses 26 and 27, the purpose of which will be explained later. Aflording constant communication of the recess 26 with the atmosphere, there is a passage 28, while the recess 27 is also in constant communication with the atmosphere through another passage 29.

Disposed within the feed tube 14 at a convenient distance from the back head 15, there is a front head or bushing 30, being secured therein by transversely disposed bolts 31. This front head is provided with a centrally. disposed bore 32, through which a tubular feed piston rod 33 is free to slide. To prevent the escape or leakage ofthe pressure fluid between the internal wall of thetube 14 and the front head 30, or between the piston rod 33 and the internal wall of the bore 32, there is a packing 34 secured to the one side of the front head by aretainer 35. This packing is formed with a duality of lips capable material such as felt, and secured therein by a spring clip retainer 37.

One end of the rod 33 is formed with. an externally threaded portion adapted to receive, in. screw tight engagement therewith, a retainer 38 Clamped between these two last parts, there is a piston 40 having secured on each side thereof a packing 41 and 42. Reciprocably mounted within the interior of the tubular rod 33, there is a stem 43, formed with an enlarged and restricted portion constituting at their 1 intersection a shoulder 44. The nut 39 is formed 1 with an aperture 45 through which the restricted portion of the stem 43 is free to pass into the feed tube 14. This outward movement of the stem is limited by the engagement of its shoulder 44 with the nut 39. The stem43 is normally maintained in its outward position by the effort of a compression spring 46 disposed within the juriousv vibrations.

rod 33 and secured therein by any suitable means, as for instance by means of a cross pin 47. Opening into the free end of the restricted portion of the stem 43, there is a restricted port 48 leading into the side of the stem. Secured to the other end of the rod 33 by means of a screw 49, there is a lug 50 formed integral with the front end of the rock drill 10, by which the movement of the rod is transmitted to the drill.

Disposed within the back head 15, and leading from the throttle valve into the left end of the feed tube 14, there is a passage 51 adapted to be closed by the free end of the stem 43'. *Affording communication between the throttle valve and the right or front end of the'feed tube-14, there is a passage 52 and conduit 53'.

During the operation of the machine, assuming the throttle valve to be positioned. as illustrated. in Fig. 4, pressure fluid from the throttle valve.

chamber 21 is admitted into the front end of the feed tube 14, through the throttle valve passage 25, port 52 and conduit 53- Pressure fluid admitted into that portion otthe feed tube will act on the front head packing 34-and piston packing 41, thus preventing the escape of the pressure fluid from the front portion of the feed tube. The piston 40 being subjected tothe action of the pressure fluid will be driven rearwardly or toward the back head 15. The movement of the piston 40 is transmitted to the rock drill 10 by the inedium ofv the piston rod 33' and lug 50, affording, in this instance, the rearward movement of the rock drill. To permit a free rearward movement of the piston 40, the pressure fluid previously admitted into the rear portion of the feed tube as well. as the atmosphere remaining therein is free to exhaust to atmosphere through the passage 51, throttle valve recess 26 and passage or vent 28. It will be seen that-if the piston 40 were permitted to reach the end of its rearward stroke without. restriction, the piston would, strike the back head 15, causing thereby an abrupt termination of the travel of the rock'drill and imparting. to the mechanism undesirable and in- In the present construction, before the piston 40 reaches the end of its rearward stroke, the free end of the stem 43 is capable of engagement with the head 15 and adapted to close the passage 41 as shown in Fig; 5. The

" port 48 opening into the free end of the stem is capable of communication with the restricted passage 48. The relatively free exhaust of the pressure fluid through the passage 51, is now forced to take place through the restricted pas 'Lsage 48, thus permitting the fluid remaining into travel of the piston will gradually be diminished. This reduction in the speed of travel of the piston will also be transmitted to the rock drill, thus permitting the operator to notice that the piston has reached the end of its stroke. In this instance, the operator may turn the throttle valve into neutral position or in the position illustrated in Fig. 5. In this position of the. throttle valve, pressure fluid fromthe throttle valve chamber 21 is: admitted into the rear end of the feed'tub'e 14 through the throttle valve passage 24, passage 51 and restricted 'port 48. The free end of the stem 43 is still maintained in, engagement with the back head 15 by the effort of the compression spring 46. Since the admissionof. the pressure fluid is restricted through the passage 48, the piston 40 will be driven forwardly at a reduced rate of speed. When the nut 39 finally engages the shoulder 44, the stem 43 will be moved away from the back head" 15, permitting thereby a free admission of the'pressurefluid into therear endofthefeeditube 1.4-, through the passage51, and the consequen=- tial unrestricted forward movementiofthei piston 40; and. rock drill 10.

to the atmosphere via the conduit 53, passage.52, throttle valve recess 2'1 and vent 29.

Although the foregoing description is. 118055?- ther understood. that various rearrangements. of.' partsv and modification of. structural detail, may.

be resorted to without departing. from the, scope or spirit of the inventionas herein claimed.

I claim:

In a drilling apparatus,. the combinatiomwitha drillingmotor; or a fiuidactuated feeding. mesh.- anism-forsaid motor including a feed tube, a feed& ing element reciprocable within said feed tube, a member'associatedavith saidfeedingelement and said drilling motor for-transmitting..therciprocation of vthe former toithe-latter, a. throttle valve housing securedwithin one; end of saidfeed tubehaving athrottle valve rotatable therein,.passages controlled by said throttle, valve for admitting. or exhaustingpressure fiuidinto or out of said feed tube-' foractuating said feeding element, and means carried by said feeding element capable of engagement with said valvehousing for automatically and regularly. reducingithe exhaust of the pressure fluid fromsaid feed. tube whenlsaid feeding element approaches one. end thereof, re-' ducing thereby thetraveling speed. of said-feeds. ing element; 1

JOHN c. CURTIS- During. the; forward movement of the piston 40, the fluidiwithinthee front end of the feed tube/141s free tov exhaust; 

